Carbamoyl-1-(pyridinylalkyl)-1H-indoles, indolines and related analogs

ABSTRACT

This invention relates to compounds of the formula ##STR1## where R 1  -R 6 , X and Y are as defined in the specification, which are useful for the treatment of various memory dysfunctions characterized by a cholinergic deficit and thus may be indicated in the treatment of Alzheimer&#39;s disease.

This is a division of prior application Ser. No. 08/109,526 filed Aug.20, 1993, now abandoned, which is a division of application Ser. No.07/835,510 filed Feb. 14, 1992, now U.S. Pat. No. 5,264,442, which is acontinuation-in-part of application Ser. No. 07/566,724, filed Aug. 13,1990, now abandoned.

This invention relates to compounds of the formula ##STR2## where R₁ ishydrogen, loweralkyl, arylloweralkyl, loweralkenyl or loweralkynyl;

R₂ is hydrogen, loweralkyl, loweralkenyl, loweralkenyl, formyl or cyano;

R₃ is hydrogen or loweralkyl;

R₄ is loweralkyl, arylloweralkyl, cycloalkyl, aryl, heteroaryl, ##STR3##or NR₃ R₄ taken together constitute ##STR4## R₅ is hydrogen, loweralkylor aryl; R₆ is hydrogen, loweralkyl, aryl, arylloweralkyl, formyl,loweralkanoyl or arylloweralkanoyl,

X and Y are independently hydrogen, nitro, amino, halogen, loweralkyl,loweralkoxy or hydroxy; or the pharmaceutically acceptable acid additionsalts thereof, and where applicable, the geometric and optical isomersand racemic mixtures thereof.

The compounds of this invention are useful for the treatment of variousmemory dysfunctions characterized by a cholinergic deficit and thus maybe indicated in the treatment of Alzheimer's disease.

The dotted lines present in Formula (I) signifies an optional doublebond. When the double bond is present, the formula I compounds representindoles.

Throughout the specification and appended claims, a given chemicalformula or name shall encompass all geometrical and optical isomers andracemic mixtures where such isomers and mixtures exist.

Unless otherwise stated or indicated, the following definitions shallapply throughout the specification and the appended claims.

The term "loweralkyl" refers to a straight or branched chain hydrocarbonhaving from 1 to 6 carbon atoms, e.g., methyl, ethyl, propyl, isopropyl,n-butyl, neopentyl, n-hexyl, etc.

The term "cycloalkyl" refers to a monovalent substituent consisting of asaturated hydrocarbon possessing at least one carbocyclic ring of 3 to 8carbon atoms, e.g., cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,cycloheptyl, etc.

The term "aryl" refers to a phenyl group optionally monosubstituted ordisubstituted with a loweralkyl, loweralkoxy, halogen or trifluoromethylgroup.

The term "heteroaryl" refers to furanyl, thienyl, pyrrolyl or pyridinyl.

The term "alkanoyl" refers to compounds of the formula ##STR5## where Ris alkyl, e.g., acetyl.

The term "alkenyl" refers to acyclic hydrocarbons with one double bondof the general formula C_(n) H_(2n), e.g., ethylene, butylene, etc.

The term "alkynyl" refers to acyclic hydrocarbons with one triple bondof the general formula C_(n) H_(2n-2), e.g., acetylene, butyne, etc.

The term "halogen" refers to a member of the halogen family consistingof fluorine, chlorine, bromine and iodine.

The compounds of this invention are prepared in the following manner.The substituents R₁, R₂, R₃, R₄, R₅, R₆, X and Y are as defined aboveunless otherwise indicated.

Compound II of the formula ##STR6## is reacted with a haloalkylpyridinehydrochloride of the formula ##STR7## where Hal is halogen, to affordCompound III of the formula ##STR8## This reaction typically takes placein the presence of a base, such as potassium hydroxide and a solventsuch as dimethylsulfoxide or dimethylformamide at ambient temperaturefor 1 to 20 hours. Compound II is commerically available or can besynthesized from known compounds according to methods known to the art.

Compound III is hydrogenated in a routine manner, for instance, using anoble metal catalyst under a hydrogen atmosphere, to afford Compound IVof the formula ##STR9## The catalyst is selected from palladium orplatinum on carbon. The reaction typically takes place at a temperatureof about 20° C. to 70° C. for 1 to 20 hours.

Alternatively, to prepare compounds where R₁ ≠H, Compound III is reactedwith n-butyllithium and a halide of the formula R₁ -Hal, where R₁ is aspreviously defined and Hal is chlorine or bromine, to afford a compoundof the formula ##STR10## Typically, this reaction is conducted intetrahydrofuran or ether at a temperature of -80° C. to 0° C. for 1 to 6hours.

Compound IIIa is subsequently hydrogenated in a manner similar to thatdescribed above to afford Compound IV where R₁ ≠hydrogen.

Compound IV is allowed to react with an isocyanate of the formula R₄--N═C═O in the presence of a base such as potassium carbonate in asuitable solvent such as tetrahydrofuran at a temperature of about 15°C. to 50° C. for 1 to 50 hours to afford compound 1. Alternatively,compound IV is allowed to react with carbonyldiimidazole and an amine ofthe formula ##STR11## in a routine manner to afford Compound I.

The novel compounds of this invention are useful for the treatment ofvarious memory dysfunctions characterized by a cholinergic deficit, suchas that found in Alzheimer's disease and other senile dementia.

This utility is manifested by the ability of these compounds to inhibitthe enzyme acetylcholinesterease and thereby increase acetylcholinelevels in the brain.

CHOLINESTERASE INHIBITION ASSAY

Cholinesterases are found throughout the body, both in the brain and inserum. However, only brain acetylcholinesterease (AChE) distribution iscorrelated with central cholinergic innervation. This same innervationis suggested to be weakened in Alzheimer patients. We have determined invitro inhibition of acetylcholinesterase activity in rat striatumaccording to the method described below.

IN VITRO INHIBITION OF ACETYLCHOLINESTERASE ACTIVITY IN RAT STRIATUM

Acetylcholinesterase (AChE), which is sometimes called true or specificcholinesterase, is found in nerve cells, skeletal muscle, smooth muscle,various glands and red blood cells. AChE may be distinguished from othercholinesterases by substrate and inhibitor specificities and by regionaldistribution. Its distribution in the brain correlates with cholinergicinnervation and subfractionation shows the highest level in nerveterminals.

It is generally accepted that the physiological role of AChE is therapid hydrolysis and inactivation of acetylcholine. Inhibitors of AChEshow marked cholinomimetic effects in cholinergically-innervatedeffector organs and have been used therapeutically in the treatment ofglaucoma, myasthenia gravis and paralytic ileus. However, recent studieshave suggested that AChE inhibitors may also be beneficial in thetreatment of Alzheimer's dementia.

The method described below was used in this invention for assayinganticholinesterase activity. This is a modification of the method ofEllman et al., Biochem. Pharmacol. 7, 88 (1961).

PROCEDURE

A. Reagents

1. 0.05M Phosphate buffer, pH 7.2

(a) 6.85 g NaH₂ PO₄.H₂ O/100 ml distilled H₂ O

(b) 13.40 g Na₂ HPO₄.7H₂ O/100 ml distilled H₂ O

(c) add (a) to (b) until pH reaches 7.2

(d) Dilute 1:10

2. Substrate in buffer

(a) 198 mg acetylthiocholine chloride (10 mM)

(b) bring to 100 ml with 0.05M phosphate buffer, pH 7.2 (reagent 1 )

3. DTNB in buffer

(a) 19.8 mg 5,5-dithiobisnitrobenzoic acid (DTNB) (0.5 mM)

(b) bring to 100 ml with 0.05M phosphate buffer, pH 7.2 (reagent 1)

4. A 2 mM stock solution of the test drug is made up in a suitablesolvent and bring to volume with 0.5 mM DTNB (reagent 3). Drugs areserially diluted (1:10) such that the final concentration (in cuvette)is 10⁻⁴ M and screened for activity. If active, IC₅₀ values aredetermined from the inhibitory activity of subsequent concentrations.

B. Tissue Preparation

Male Wistar rats are decapitated, brains rapidly removed, corporastriata dissected free, weighed and homogenized in 19 volumes(approximately 7 mg protein/ml) of 0.05M phosphate buffer, pH 7.2, usinga Potter-Elvehjem homogenizer. A 25 microliter aliquot of the homogenateis added to 1 ml of vehicle or various concentrations of the test drugand preincubated for 10 minutes at 37° C.

C. Assay

Enzyme activity is measured with the Beckman DU-50 spectrophotometer.This method can be used for IC₅₀ determinations and for measuringkinetic constants.

Instrument Settings

Kinetics Soft-Pac Module #598273 (10)

Program #6 Kindata:

Source--Vis

Wavelength--412 nm

Sipper--none

Cuvettes--2 ml cuvettes using auto 6-sampler

Blank--1 for each substrate concentration

Interval time--15 seconds (15 or 30 seconds for kinetics)

Total time--5 minutes (5 or 10 minutes for kinetics)

Plot--yes

Span--autoscale

Slope--increasing

Results--yes (gives slope)

Factor--1

Reagents are added to the blank and sample cuvettes as follows:

Blank: 0.8 ml Phosphate Buffer/DTNB 0.8 ml Buffer/Substrate

Control: 0.8 ml Phosphate Buffer/DTNB/Enzyme 0.8 ml PhosphateBuffer/Substrate

Drug: 0.8 ml Phosphate Buffer/DTNB/Drug/Enzyme 0.8 ml PhosphateBuffer/Substrate

Blank values are determined for each run to control non-enzymatichydrolysis of substrate and these values are automatically substractedby the kindata program available on kinetics soft-pac module. Thisprogram also calculates the rate of absorbance change for each cuvette.

For IC₅₀ Determinations:

Substrate concentration is 10 mM diluted 1:2 in assay yielding finalconcentration of 5 mM. DTNB concentration is 0.5 mM yielding 0.25 mMfinal concentration ##EQU1##

IC₅₀ values are calculated from log-probit analysis. Results of thisassay for representative compounds of this invention and physostigmineare presented in Table 1.

                  TABLE 1                                                         ______________________________________                                        Inhibition of Brain Acetylcholinesterase Activity                                                 Inhibitory Concentration                                  Compound            IC.sub.50 (μM)                                         ______________________________________                                        1-(4-pyridinylmethyl)-1H-indol-                                                                   6.83                                                      5-yl methylcarbamate                                                          1-(4-pyridinylmethyl)-1H-indol-                                                                   12.48                                                     5-yl phenylmethylcarbamate                                                    Physostigmine (Reference compound)                                                                0.006                                                     ______________________________________                                    

This utility is further demonstrated by the ability of these compoundsto restore cholinergically deficient memory in the Dark Avoidance Assaydescribed below.

DARK AVOIDANCE ASSAY

In this assay mice are tested for their ability to remember anunpleasant stimulus for a period of 24 hours. A mouse is placed in achamber that contains a dark compartment; a strong incandescent lightdrives it to the dark compartment, where an electric shock isadministered through metal plates on the floor. The animal is removedfrom the testing apparaus and tested again, 24 hours later, for theability to remember the electric shock.

If scopolamine, an anticholinergic that is known to cause memoryimpairment, is administered before an animal's initial exposure to thetest chamber, the animal re-enters the dark compartment shortly afterbeing placed in the test chamber 24 hours later. This effect ofscopolamine is blocked by an active test compound, resulting in agreater interval before re-entry into the dark compartment.

The results for an active compound am expressed as the percent of agroup of animals in which the effect of scopolamine is blocked, asmanifested by an increased interval between being placed in the testchamber and re-entering the dark compartment.

Results of this assay for representative compounds of this invention andthose for tacrine and pilocarpine (reference compounds) are presented inTable 2.

                  TABLE 2                                                         ______________________________________                                                     Dose (mg/kg                                                                              % of Animals with                                                  of body    Scopolamine-Induced                                   Compound     weight, s.c.)                                                                            Memory Deficit Reversal                               ______________________________________                                        1-[1-(4-pyridinyl-                                                                         1.0        20%                                                   butyl)]-1H-indol-5-yl-                                                        methylcarbamate                                                               Tacrine      0.63       13%                                                   ______________________________________                                    

Effective quantities of the compounds of the present invention may beadministered to a subject by any one of various methods, for example,orally as in capsules or tablets, parenterally in the form of sterilesolutions or suspensions, and in some cases intravenously in the form ofsterile solutions. The compounds of the present invention, whileeffective themselves, may be formulated and administered in the form oftheir pharmaceutically acceptable addition salts for purposes ofstability, convenience of crystallization, increased solubility and thelike.

Preferred pharmaceutically acceptable addition salts include salts ofinorganic acids such as hydrochloric, hydrobromic, sulfuric, nitric,phosphoric and perchloric acids; as well as organic acids such astartaric, citric, acetic, succinic, maleic, fumaric, and oxalic acids.

The active compounds of the present invention may be administeredorally, for example with an inert diluent or with an edible carrier.They may be enclosed in gelatin capsules or compressed into tablets. Forthe purpose of oral therapeutic administration, the compounds may beincorporated with excipients and used in the form of tablets, troches,capsules, elixirs, suspensions, syrups, wafers, chewing gums and thelike. These preparations should contain at least 0.5% of activecompound, but may be varied depending upon the particular form and mayconveniently be between 4% to about 75% of the weight of the unit. Theamount of compound present in such composition is such that a suitabledosage will be obtained. Preferred compositions and preparationsaccording to the present invention are prepared so that an oral dosageunit form contains between 1.0-300 mgs of active compound.

The tablets, pills, capsules, troches and the like may also contain thefollowing ingredients: a binder such as microcrystalline cellulose, gumtragacanth or gelatin; an excipient such as starch or lactose, adisintegrating agent such as alginic acid, Primogel™, corn starch andthe like; a lubricant such as magnesium stearate or Sterotex®; a glidantsuch as colloidal silicon dioxide; and a sweetening agent such assucrose or saccharin or a flavoring agent such as peppermint, methylsalicylate, or orange flavoring may be added. When the dosage unit formis a capsule, it may contain, in addition to materials of the abovetype, a liquid carrier such as fatty oil. Other dosage unit forms maycontain other various materials which modify the physical form of thedoseage unit, for example, as coatings. Thus tablets or pills may becoated with sugar, shellac, or other enteric coating agents. A syrup maycontain, in addition to the active compounds, sucrose as a sweeteningagent and certain preservatives, dyes and colorings and flavors.Materials used in preparing these various compositions should bepharmaceutically pure and non-toxic in the amounts used.

For the purpose of parenteral therapeutic administration, the activecompounds of the invention may be incorporated into a solution orsuspension. These preparations should contain at least 0.1% of theaforesaid compound, but may be varied between 0.5 and about 30% of theweight thereof. The amount of active compound in such compositions issuch that a suitable dosage will be obtained. Preferred compositions andpreparations according to the present invention are prepared so that aparenteral dosage unit contains between 0.5 to 100 mgs of activecompound.

The solutions or suspensions may also include the following components;a sterile diluent such as water for injection, saline solution, fixedoils, polyethylene glycols, glycerine, propylene glycol or othersynthetic solvents; antibacterial agents such as benzyl alcohol ormethyl parabens; antioxidants such as ascorbic acid or sodium bisulfite;chelating agents such as ethylenediaminetetraacetic acid; buffers suchas acetates, citrates or phosphates and agents for the adjustment oftonicity such as sodium chloride or dextrose. The parenteral preparationcan be enclosed in ampules, disposable syringes or multiple dose vialsmade of glass or plastic.

Examples of the compounds of the invention are listed below:

1-(4-pyridinylmethyl)-1H-indol-5-yl methylcarbamate;

1-(4-pyridinylmethyl)-1H-indol-5-yl butylcarbamate;

1-(4-pyridinylmethyl)-1H-indol-5-yl phenylmethylcarbamate;

1-[1-(4-pyridinylbutyl)]-1H-indol-5-yl methylcarbamate;

1-[1-(4-pyridinylbutyl)]-1H-indol-5-yl phenylmethyl carbamate;

3-methyl-1-(4-pyridinylmethyl)-1H-indol-5-yl methylcarbamate;

1-[1-(3-fluoro-4-pyridinyl)butyl]-1H-indol-5-yl ethylcarbamate;

1-[1-(4-pyridinylbutyl)]-1H-indol-5-yl dimethylcarbamate;

6-fluoro-1-(4-pyridinylmethyl)-1H-indol-5-yl butylcarbamate;

1-[1-(3-fluoro-4-pyridinyl)butyl]-3-methyl-1H-indol-5-ylmethylcarbamate;

2,3-dihydro-1-(4-pyridinylmethyl)-1H-indol-5-yl methylcarbamate;

2,3-dihydro-1-[1-(4-pyridinylbutyl)]-1H-indol-5-yl methylcarbamate;

2,3-dihydro-1-[1-(3-fluoro-4-pyridinyl)butyl]-1H-indol-5-ylmethylcarbamate;

2,3-dihydro-1-(4-pyridinylmethyl)-1H-indol-5-yl dimethylcarbamate;

1-[1-(4-pyridinylbutyl)]-1H-indol-5-yl 2-phenylcyclopropylcarbamate;

1-[1-(4-pyridinylpropyl)]-1H-indol-5-yl cyclohexylcarbamate;

3-ethyl-1-(3-fluoro-4-pyridinylmethyl)-1H-indol-5-yl(4-phenylmethylpiperazinyl)carbamate;

1-[1-(4-pyridinylbutyl)]-1H-indol-5-yl piperidinylcarbamate;

1-[1-(3-fluoro-4-pyridinylpropyl)]-1H-indol-5-yl morpholinylcarbamate;

2,3-dihydro-1-[1-(4-pyridinylpropyl)]-1H-indol-5-yl cyclohexylcarbamate;

2,3-dihydro-1-[1-(4-pyridinylpropyl)]-1H-indol-5-yl2-phenylcyclopropylcarbamate;

2,3-dihydro-1-[1-(3-fluoro-4-pyridinylpropyl)]-1H-indol-5-ylpiperidinylcarbamate; and

2,3-dihydro-6-fluoro-1-(4-pyridinylbutyl)-1H-indol-5-yl methylcarbamate,

The following examples are for illustrative purposes and are not to beconstrued as limiting the invention disclosed herein. All temperaturesare given in degrees centigrade (°C.) unless indicated otherwise.

EXAMPLE 1 1-(4-Pyridinylmethyl)-1H-indol-5-yl methylcarbamate

To a solution of 1-(4-pyridinylmethyl)-1H-indol-5-ol (2.4 g) in 50 mltetrahydrofuran, was added milled K₂ CO₃ (1.5 g), followed by methylisocyanate (0.65 ml). After stirring at ambient temperature for threehours, the mixture was filtered and the filtrate evaporated to a solid,3.0 g, m.p. 170° C. This material was eluted on a silica gel column with2% methanol/dichloromethane via high pressure liquid chromatography(HPLC) and the desired fractions were combined, then evaporated to yield2.4 g of 1-(4-pyridinylmethyl)-1H-indol-5-yl methylcarbamate, as asolid, m.p. 179°-180° C.

Analysis: Calculated for C₁₆ H₁₅ N₃ O₂ : 68.31% C 5.38% H 14.94% NFound: 68.28% C 5.47% H 14.97% N

EXAMPLE 2 1-(4-Pyridinylmethyl)-1H-indol-5-yl butylcarbamatehydrochloride

To a solution of 1-(4-pyridinylmethyl)-1H-indol-5-ol (3.0 g) in 50 mltetrahydrofuran, was added milled K₂ CO₃ (1.8 g) followed by butylisocyanate (1.5 ml). After stirring at ambient temperature for fourhours, the mixture was filtered, and the filtrate evaporated to an oil,(.sup.˜ 4.5 g) which was eluted on a silica gel column with ethylacetate/dichloromethane (1:1) via HPLC. The desired fractions werecombined and evaporated to yield 3.6 g of a solid, m.p. 135°-137° C.This material was dissolved in methanol, the pH adjusted to 1 withethereal-HCl and diluted with ether. The resultant precipitate wascollected and dried to give 3.0 g of 1-(4-pyridinylmethyl)-1H-indol-5-ylbutylcarbamate hydrochloride, m.p. 230° C. (dec).

Analysis: Calculated for C₁₉ H₂₁ N₃ O₂.HCl: 63.41% C 6.16% H 11.68% NFound: 63.48% C 6.18% H 11.68% N

EXAMPLE 3 1-(4-Pyridinylmethyl)-1H-indol-5-yl phenylmethylcarbamate

To a solution of 1-(4-pyridinylmethyl)-1H-indol-5-ol (2.2 g) in 50 mltetrahydrofuran, was added milled K₂ CO₃ (1.4 g) followed byphenylmethyl isocyanate (1.2 ml). After stirring at ambient temperaturefor twenty hours, the mixture was filtered, and the filtrate evaporatedto an oil, (¹⁸ 3.5 g) which was eluted on a silica gel column with ethylacetate/dichloromethane (1:1) via HPLC. The desired fractions werecombined and evaporated to yield 2.8 g of1-(4-pyridinylmethyl)-1H-indol-5-yl phenylmethylcarbamate, m.p.112°-114° C.

Analysis: Calculated for C₂₂ H₁₉ N₃ O₂ : 73.93% C 5.36% H 11.76% NFound: 73.90% C 5.45% H 11.68% N

EXAMPLE 4 1-[1-(4-Pyridinylbutyl)]-1 H-indol-5-yl methylcarbamate

To a solution of 1-[1-(4-pyridinylbutyl)]-1H-indol-5-ol(2.4 g) in 50 mltetrahydrofuran, was added milled K₂ CO₃ (1.3 g) followed by methylisocyanate 0.53 ml). After stirring at ambient temperature for threehours, the mixture was filtered, and the filtrate evaporated to an oil(3.0 g) which was eluted on a silica gel column with ethyl acetate viaHPLC. The desired fraction was evaporated to yield 2.2 g of1-[1-(4-pyridinylbutyl)]-1H-indol-5-yl methylcarbamate, as a solid, m.p.128°-9° C.

Analysis: Calculated for C₁₉ H₂₁ N₃ O₂ : 70.56% C 6.55% H 12.99% NFound: 70.31% C 6.42% H 12.87% N

EXAMPLE 5 1-[1-(4-Pyridinylbutyl)]-1H-indol-5-yl phenylmethylcarbamate

To a solution of 1-[1-(4-pyridinylbutyl)]-1H-indol-5-ol (2.2 g) in 50 mltetrahydrofuran, was added milled K₂ CO₃ (1.29 g), followed byphenylmethyl isocyanate 1.0 ml). After stirring at ambient temperaturefor twenty hours, the mixture was filtered, and the filtrate evaporatedto an oil, (3.3 g) which was eluted on a silica gel column with ethylacetate/dichloromethane (1:1) via HPLC. The desired fraction wasevaporated to yield 2.6 g of 1-[1-(4-pyridinylbutyl)]-1H-indol-5-ylphenylmethylcarbamate, as a solid, 119°21° C.

Analysis: Calculated for C₂₅ H₂₅ N₃ O₂ : 75.16% C 6.31% H 10.52% NFound: 75.11% C 6.39% H 10.47% N

We claim:
 1. A compound of the formula ##STR12## where R₁ is hydrogen,loweralkyl, arylloweralkyl, loweralkenyl or loweralkynyl;R₂ is hydrogen,loweralkyl, loweralkenyl, formyl or cyano; ##STR13## R₅ is hydrogen,loweralkyl or aryl; R₆ is hydrogen, loweralkyl, aryl, arylloweralkyl,formyl, loweralkanoyl or arylloweralkanoyl, X and Y are independentlyhydrogen, nitro, amino, halogen, loweralkyl, loweralkoxy or hydroxy; theterm aryl in each occurrence signifying a phenyl group optionally mono-or disubstituted with a loweralkyl, loweralkoxy, halogen ortrifluoromethyl group; the term cycloalkyl in each occurrence signifyinga carbocyclic ring of 3 to 8 carbon atoms; or the pharmaceuticallyacceptable acid addition salts thereof, and where applicable, thegeometric and optical isomers and racemic mixtures thereof.
 2. Apharmaceutical composition comprising a compound as defined in claim 1in an amount effective for alleviating a memory dysfunctioncharacterized by a cholinergic deficit and a pharmaceutically acceptablecarrier therefor.
 3. A method of treating a patient in need of relieffrom a memory dysfunction characterized by a cholinergic deficit whichcomprises administering to such a patient an effective amount of acompound as defined in claim 1.